The invention is a door construction for a motor vehicle which comprises a body and an internal support system. In this case, the door means not only the side doors but also that of the rear flaps and the trunk lid of a motor vehicle.
The body of the traditional motor vehicle doors consists mainly of an outer shell and an inner shell, as well as other sheet metal parts for reinforcement and to support auxiliary installations, e.g. window channels and window winders. The inner shell forms the front of the door all around which is joined to the outer shell by means of spot welding. In case there is a door with a window frame, both shells together also constitute the same.
A large area of the inner shell is mostly opened to enable space for the auxiliary installations. Reinforcement supports or reinforcement frames of metal are generally provided as the supporting system, especially for strengthening in case of a collision. However, these are heavy and collide with the window channels, thus insufficient as passenger protection because of their limited effect.
Generally, despite the relatively heavy weight of these types of traditional doors, the specific susceptibility of energy is insufficient, especially the non-fulfillment of the future statutory rules, their rigidity and structure consistency (e.g. when the motor vehicle and the door are distorted), the manufacturing costs are high because of the complex construction and the expensive fastening of the auxiliary installations. The soundproofing and the thermal insulation are also poor.
Door constructions with plastic parts have acquired a reputation. In the DE 4407731 there is a door which consists of two or three shells made of a fiber compound material which are welded to one another. There is a detachable one fastened to this outer shell. The disadvantages of this are the complicated shape of the shells made of a compound material which practically shapes the whole door for the hinges and the lock as well as the efforts involved to establish a connection by applying adhesive or high frequency welding. Despite the supports, the rigidity and the intrusion resistance in case of a side collision affecting the door is insufficient. The detachable outer shell cannot contribute to the reinforcement and the natural stability of the door. In addition, this solution means complete deviation from the usual door constructions which requires the new construction of a door.
In the EP 712 746 A there is a support system for a door which can bear all auxiliary aggregates and can then be fitted into the door. However, it consists of extruded plastic and does not offer any special reinforcement of the door structure.
In the DE 31 02 329 there is a multi-component door by which the center part of the support system comprises the inner and outer plates of the door. The center part of the door has a torsion-proof compound plastic body of a shearing modulus of elasticity which covers a large area with one of its two shells enclosed by a core of rigid expanded polyurethane in which at least one energy absorption body is imbedded. The core of expanded polyurethane gives the compound plastic body a certain rigidity by counteracting bending, using horizontal transverse force, which, however, is insufficient in case of collision. For this reason an energy absorption body is imbedded, the resistance of which has the effect which opposes the core of the rigid expanded polyurethane by an elongation of the bicurve profile diaphragm. Such an elongation and thus the energy absorbing effectxe2x80x94only occurs in the case of collision when there is extreme deflection inside the motor vehicle for which there is no space in the door. Even the extreme thickness of the compound plastic body cannot change this. Therefore it is necessary to use this body as a support of the inner and outer plates of the door. Normally the inner and outer plates of the door support the inner reinforcement. This reverse function requires a complete new development of the entire door and excludes further development of the existing one.
The invention is thus to be based on the task to propose an especially light door construction which connects the maximum natural rigidity in all directions as well as maximum energy absorption and intrusion resistance by simple mounting of the complete door and does not require to deviate from the traditional basic construction of a door.
This will be achieved in the invention by the following characteristics:
a) fins connected to one another and directed inwards in longitudinal direction on the inner and outer walls
b) fins which create spaces, where one of which at least will have a compression-proof filling
c) inner and outer walls connected to one another at their contour and where accommodations have been made for fastening by which the support system shall be fastened to the body of the door
According to the invention a laminated body will be installed in the traditional body of the door which takes up a large part of the door surface and on which all auxiliary aggregates can be mounted in addition. Such a body is spacious due to its double wall and achieves an especially high bending resistance and torsion rigidity due to the ribs which are directed inwards in a longitudinal direction and which are connected to each other as well as due to the compression-proof filling. Owing to the distribution of percussive power on a larger surface the depth of penetration is kept at a minimum in the case of collision and bends in the zone of pressure is counteracted.
By using fiber-reinforced plastics even the contour, the shape and construction of the inner wall and the outer wall also deviating from the plane surface by arrangement and alignment of the reinforced fiber can be based on the stress and the shape if the respective door and adapted to the position of the fastening points.
Accommodations for fastening will be considered on the contour of the support system where it will not impair the body quite as much and which enables the largest possible distance between the fastening points. Due to the connection along the entire contour, not only will be highest torsion rigidity be achieved, but it will also prevent moisture from entering. As the fastening to the body of the door will only be done at points above the integrated provisions, the forces will be passed on in a controlled manner and installation can be effected simply and without assiduous adjustments, even in one of the traditional door bodies which has been only slightly modified.
In a profitable development of the invention, there will be a light compression-proof core material between the inner and outer walls which can also be sound-proof. Such a material increases the buckling rigidity and the intrusion resistance in case of a collision across the level of the door. This core material can have a honeycomb structure or be of foam. When this is thermally activated, an internal overpressure can be achieved by pressing which further increases the rigidity. The core material can also be of a light wood (e.g. balsa wood), which also has the advantage of being a good sound-proof as well as thermal insulation.
To further improve the collision behaviour the walls in zones exposed to stress could be provided with reinforcements which are orientated and dimensioned accordingly. These could be of metal and also imbedded in the matrix. If the reinforcements are provided with high tensile reinforcement fibers (perhaps of Kevlar), the energy absorption values of deformation will be achieved which satisfy the most stringent requirements of the future or show a very low thickness in case of similar strength.
In one of the favourable designs, threaded bushings whose thread axis is in the longitudinal direction will be provided for fastening. Due to this the fastening points of the body are easy for mounting to the front walls of the body of the door.
Accommodations shall be made for fastening on the points of the hinge joints and the door lock so that the line of force is kept away from the body of the door. If accommodations for fastening are made with lateral shoulders around which the reinforced fiber or prepregs are arranged, which causes direct introduction of force from the fastening means in the fibers without impairing them. This is, still to be demonstrated, important when applying initial stress during manufacture.
The subject of the invention is also a process for the manufacture of doors and covers for a motor vehicle, which shall be effected as follows:
a) Applying prepregs which can be draped and if necessary the reinforcements of the inner and outer walls in the mould
b) Placing the core material in the appropriate spaces
c) Applying prepregs which can be draped and if necessary the reinforcements of the inner and outer walls
d) Placing the accommodations
e) Closing of the mould and pressing it together at increased temperature
In order to prestress the walls of the support systemxe2x80x94like a prestressed concrete bridgexe2x80x94and to enable it to have an especially high rigidity, the holding fixtures will be arranged in a displaced manner and their shoulders will be surrounded by the ends of individual prepregs, after closing the mould tension will be applied on the accommodations from the outside by which these will be brought to the intended position, thereby prestressing the prepregs and the temperature will then be increased.